Start EAP 6.3
Deploy Metamer/Showcase
Whichever you prefer, both have similar push examples.
In Chrome open dev tools
Switch to 'Network'
Use pre-defined filter 'WebSockets'
Go to page with push
Link to page in Metamer
Link to page in Showcase
As you enter the page in dev tools there should be a request but there is none
If you clear the filter (to see all network activity) you can notice that new requests are constantly created - which is the old method without WebSockets

Description

When using push, connection should be established via WebSockets.
This does not happen and the old method is used. I also tried a workaround which was needed in earlier versions of EAP - manually enabling websockets.

I used EAP 6.3 and Metamer/Showcase. Please see steps to reproduce.

As for verification of WebSockets usage, Chrome dev tools can detect connection establishment as described here.